1. Technical Field
This disclosure relates to an image forming apparatus, and more specifically to an image forming apparatus including a recording head to eject liquid droplets.
2. Description of the Background Art
Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having two or more of the foregoing capabilities. As one type of image forming apparatus employing a liquid-ejection recording method, an inkjet recording apparatus is known that uses a recording head formed with a liquid ejection head (liquid-droplet ejection head) for ejecting droplets of ink. During image formation, the image forming apparatuses eject droplets of ink or other liquid from the recording head onto a recording medium to form a desired image.
Such inkjet-type image forming apparatuses fall into two main types: a serial-type image forming apparatus that forms an image by ejecting droplets from the recording head while moving the recording head in a main scanning direction of the carriage, and a line-head-type image forming apparatus that forms an image by ejecting droplets from a linear-shaped recording head held stationary in the image forming apparatus.
The serial-type image forming apparatus may include, for example, a linear encoder to detect the movement of a carriage mounted with a recording head. The linear encoder includes an encoder scale disposed parallel to the main scanning direction of the carriage and an encoder sensor formed with an optical sensor mounted on the carriage. Further, a rotary encoder is provided in the same manner to control sheet feeding.
In such an image forming apparatus employing a liquid ejection head, ink mist arises in ejecting liquid droplets for image formation and can obscure the scale marks, thus preventing precise positional control of the carriage and/or positional and speed control of sheet feeding.
To counteract the above-described effect, in one known approach a side face of the carriage is formed so as to guide airflow carrying ink mist toward an area in which an optical detection unit is not disposed. In another approach, for example, ink mist is suctioned into a hollow guide rod for guiding the carriage. Alternatively, the ink mist is suctioned using a suction unit or absorbed by an absorber.
However, the above-described approaches are not completely effective. Thus, for example, in a case in which at least one side face of a carriage is shaped to guide airflow, the ink mist is guided toward the front side of the carriage and consequently continuously stirred up, thus adhering to the encoder scale.